Display all testnet tokens

[michele-franchi]

Acceptance criteria:

• On testnet all tokens in the /tokens page are visible
• The dropdown "Listed" / "All tokens" is hidden
• If the token name is empty (also in the details page):
  • A gray text "Empty name" is displayed
• If the token symbol is empty (also in the details page):
  • A gray text "Empty symbol" is displayed